Rebuilding front Master cylinder on my '79

[Rolls]

Great tips on the metal plate and the ATE type 200. Thanks!!

Calipers coming along...

[bern45]

If you got the new reservoir cap with the cup kit, don't forget to remove the metal frame from the old cap and install it on the new one, otherwise it will spill brake fluid all over you fuel tank when you go for a ride (ask me how I know....)
Fernando.

We will be rebuilding the master cylinder on the CBX as well right after we finished installing the Moto metal wheels and new tires on the current truck project. I'll keep that and other tips in mind.

[wyly]

I'm hoping with the freshened mc and new black stainless lines, the brakes will cooperate so I can ride this over to DMV and get it authorized to be ridden on the street. It'll need new front pads, so I'll do the calipers and maybe fresh caliper pistons after I get plates on it. Heavy bike and treacherous mountain roads spells tip-top brakes and tires to my way way of thinking.

if you want an easy brake upgrade convert to twin pots...a number of mid 80's hondas will fit, I got mine from a salvaged 84 or 86 Cb750 and then added full sintered pads... you'll need the hangers as well and they're a straight swap, easy peasy ....I converted front and back, significantly better stopping power...

[Mike Cecchini]

If you never want to rebuild the brake system again and have beautiful brakes for decades, then switch to DOT5
now. I did mine 10+ yrs ago as well as several other X's. Fluid changes every 5--10 yrs and it comes out clean and clear just like new.

Good for track days too unless you are within 20 secs of lap record. Then you should use DOT 4.

[Larry Zimmer]

Thing to know/remember: If changing to DOT 5 be CERTAIN to purge the system and clean EVERYTHING well. DOT 5 does not play well with any of the other DOTS!! For all the rubber parts in a change-over the best bet is to just get new.

[Mike Cecchini]

Actually DOT 5 was designed to mix with all other DOT 3, 4 and 5.1 brake fluids. It's only BREMBO brake systems you have to worry about the (natural) rubber seals. Brembo brake systems MUST be rebuilt with totally virgin rubber that has never seen or used DOT 3, 4 or 5.1 brake fluid. Then and only then can you put DOT 5 into a Brembo system. I've been doing it for 20+ yrs.....zero issues.

Japanese bikes use man made rubber so zero issues in all our CBX's. No need to flush or drain DOT 3, 4 or 5.1. Just put the DOT 5 in and bleed the system. Few months later when the little bit of DOT 3 or 4 has thuroughly mixed with the DOT 5, just do a quick bleed again so there's 100% DOT 5 in the system.

[EMS]

Here we go again....

It is not only the rubber and seals that act up. The fluids actually do not play well with each other. If you mix a silicone based fluid with DOT3/4/5a it will react with the old fluid and precipitate, clogging up the system.
Anybody who wants to follow the advice of Mr C., you are welcome to do so. just be aware of possible issues.

Here is just one example what others have to say:

DOT5:

It does NOT mix with DOT3 or DOT 4 or DOT 5.1. Most reported problems with DOT 5 are probably due to some degree of mixing with other fluid types. A residue of the former non-compatible fluid is sufficient to cause serious issues. The best way to convert to DOT 5 is to totally rebuild the hydraulic system. Additionally, the same advice applies if switching from Dot 5 to any of the other fluids.

Since DOT 5 does not absorb water, any moisture in the hydraulic system will "puddle" in one place. This can cause localized corrosion in the hydraulics.

Careful bleeding is required to get all of the air out of the system. It is hard to you without introducing bubbles and thus results in soft pedal feel. These small bubbles will form large bubbles over time. It may be necessary to do a series of bleeds.

DOT 5 is less compressible (often creating a slightly softer pedal). It is not recommended for racing application.
It is hard to pour without introducing bubbles and thus results in soft pedal feel,

It is not recommended by the brake manufacturer, especially for ABS brakes.

It is about twice as expensive as DOT 4 fluid.

So silicone fluid aerates easily. Harley-Davison, one of the sole current OEM users of silicone fluid, warns buyers to let the fluid sit at least an hour before using it. If shaken on the way home, it will aerate enough to look like a freshly poured soft drink. Silicone fluid is also slightly more compressible than glycol fluid, does not change color to tip the user to its moisture content, and worst of all, neither accepts or disperses moisture, making systems using it more corrosion prone, and requiring much more frequent fluid changes. Silicone brake fluid also lacks glycol fluid's naturally occurring lubricity, making it incompatible with the mechanical valving in some anti-lock braking systems.

[Mike Cecchini]

For the record, when Dow Corning engineered and designed DOT 5 silicone brake fluid in 1985, it was a US Federal Dept. of Transportation regulation that DOT 5 be compatible with all DOT 3 & 4 brake fluids at the time. Dot 5.1 had not been designed or produced then. This said........to this day ALL DOT 5 brake fluids are 100% compatible with all DOT 3, 4 & 5.1 brake fluids....to this day. The reasons are obvious as US brake fluid makers and the Dept of Transportation wanted no issues or problems with DOT 5 brake fluid.

The proof of all this is I and many of the motorcycle and car shops in the Washington DC area have been installing DOT 5 successfully since the 1980's without issue. I have personally installed DOT 5 in many cars and many motorcycles of all different makers and models. Zero issues in 33 yrs.

Brembo brake systems can also be done, but you MUST replace all rubber components with new virgin rubber components and the brake system flushed with denatured alcohol to remove all traces . Then only use DOT 5 from that point onwards.

For the CBX all you need to do is pour it in and bleed the system until all the old brake fluid is removed. I did this on my CBX 12 yrs ago and several other CBX owners here have done the same with zero issues and perfect results.

You can do as you like for your CBX, but if you want never to have to rebuild your brake system because of all the corrosion DOT 3, 4 and 5.1 will allow, then DOT 5 is what you want.

[FalldownPhil]

Eeeeeeeeeeek !!
Can't we just do an oil thread

[NobleHops]

If you got the new reservoir cap with the cup kit, don't forget to remove the metal frame from the old cap and install it on the new one, otherwise it will spill brake fluid all over you fuel tank when you go for a ride (ask me how I know....)
Fernando.

This. Feel free to ask me too.

[Larry Zimmer]

As always -- those little things are the great contributions. Thanks, guys.

[thomasgeorgi]

So I've been trying to bleed my newly rebuilt front brake system and at a break skimmed this thread. Someone should post that bit about the metal frame under the reservoir cap in BIG CAPITAL LETTERS. I didn't know about this and noticed a slight seepage in very short order. Thank for letting me know. As far as rust and that pesky aluminum corrosion I've found this stuff called EVAPO-RUST at Walmart which cleans up both really good. Drop the part in and let it soak for a couple days and you may be surprised. I was.

[Larry Zimmer]

Another good rust dissolver is Metal Rescue. Similar to Evap0Rust. (For those who can't Evapo-Rust.) Both are great in that they don't affect paint. And, they DO remove rust. (Iron rust, that is.)